Sheet detecting apparatus, sheet conveying apparatus, and image forming apparatus

Abstract

A sheet detecting apparatus has an abutment member against which a leading edge of a conveyed sheet abuts, a holding member with a positioning portion to hold the abutment member, and an indicator flag moving in association with movement of the abutment member. The abutment member moves between an abutment position and a retracted position, the holding member moves between a first position and a second position retracted from the first position, the abutment member is pushed by the leading edge of the sheet when the holding member is at the first position, with the push moving the holding member to the second position, the holding member is moved in a direction away from the first position so that the leading edge of the sheet is separated from the abutment surface, and the holding member moves from the second position to the first position when the abutment member is pushed by the sheet to the retracted position.

The invention claimed is: 
     
       1. A sheet detecting apparatus configured to detect a sheet on a sheet conveying path on which the sheet is conveyed, the sheet detecting apparatus comprising:
 an abutment member having an abutment surface against which a leading edge of a sheet being conveyed abuts; 
 a holding member movable between a first position at which the holding member is located with respect to a locating portion provided in a main body of the sheet detecting apparatus and a second position at which the holding member is retracted from the first position; and 
 a flag configured to move in association with movement of the abutment member in order to change indication of detection by a detecting portion, 
 wherein the holding member holds the abutment member so that the abutment member is movable between a located state in which a striking portion provided on the abutment member strikes against a regulating portion provided on the holding member to locate the abutment member with respect to the holding member and a separated state in which the striking portion and the regulating portion are separated from each other, and 
 wherein in a state in which the holding member is located in the first position and the abutment member is in the located state, the leading edge of the sheet abuts against the abutment surface to push the abutment surface to move the holding member from the first position to the second position while the abutment member is in the located state, and thereafter, when the leading edge of the sheet separates from the abutment surface, the abutment member is moved from the located state to the separated state. 
 
     
     
       2. A sheet detecting apparatus according to  claim 1 , further comprising a first urging portion configured to urge the holding member. 
     
     
       3. A sheet detecting apparatus according to  claim 2 , further comprising a second urging portion configured to urge the abutment member. 
     
     
       4. A sheet detecting apparatus according to  claim 2 , wherein in a case where the holding member is moved from the first position to the second position, the holding member is moved against an urging force of the first urging portion. 
     
     
       5. A sheet detecting apparatus according to  claim 1 , wherein the abutment member is rotatable about a first rotary shaft with respect to the holding member. 
     
     
       6. A sheet detecting apparatus according to  claim 5 , wherein the holding member is rotatable about a second rotary shaft different from the first rotary shaft. 
     
     
       7. A sheet detecting apparatus according to  claim 1 , further comprising a conveying portion configured to form a nip portion to nip and convey the sheet, wherein in a case where the holding member is located at the first position, the abutment surface of the abutment member is located upstream of the nip portion in a sheet conveying direction. 
     
     
       8. A sheet detecting apparatus according to  claim 7 , wherein the conveying portion comprises a roller pair including a first roller and a second roller, and
 wherein the holding member is provided on a side of the second roller. 
 
     
     
       9. A sheet detecting apparatus according to  claim 6 , wherein in a state in which the sheet is nipped by the nip portion and the holding member is located at the second position, the abutment member is located closer to the side of the second roller than the first roller. 
     
     
       10. A sheet detecting apparatus according to  claim 1 , wherein the abutment member is provided in each position of a plurality of positions in a width direction intersecting with a sheet conveying direction. 
     
     
       11. A sheet detecting apparatus according to  claim 1 , further comprising a stopper configured to position the holding member in the first position. 
     
     
       12. An image forming apparatus comprising:
 a sheet detecting apparatus; and 
 an image forming portion configured to form an image on a sheet, 
 the sheet detecting apparatus comprising:
 an abutment member having an abutment surface against which a leading edge of a sheet being conveyed abuts; 
 a holding member movable between a first position at which the holding member is located with respect to a locating portion provided in a main body of the sheet detecting apparatus and a second position at which the holding member is retracted from the first position; and 
 a flag configured to move in association with movement of the abutment member in order to change an indication of detection by a detecting portion, 
 
 wherein the holding member holds the abutment member so that the abutment member is movable between a located state in which a striking portion provided on the abutment member strikes against a regulating portion provided on the holding member to locate the abutment member with respect to the holding member and a separated state in which the striking portion and the regulating portion are separated from each other, and 
 wherein in a state in which the holding member is located in the first position and the abutment member is in the located state, the leading edge of the sheet abuts against the abutment surface to push the abutment surface to move the holding member from the first position to the second position while the abutment member is in the located state, and thereafter, when the leading edge of the sheet separates from the abutment surface, the abutment member is moved from the located state to the separated state.